The phrase "buoy up" is typically used to describe an act of providing support, encouragement, or hope to someone who is feeling down or discouraged. There are several synonyms that can be used to convey a similar meaning, including: uplift, inspire, boost, motivate, encourage, embolden, hearten, bolster, cheer, and invigorate. Each of these words carries a slightly different connotation and may be more appropriate in certain contexts or situations. For example, "uplift" may be used to convey a sense of lifting someone's spirits, while "motivate" may connote giving someone a reason to continue on or overcome a challenge. Regardless of the specific word chosen, the intention is to provide a sense of support and positivity to the person in need.